Photovoltaics are in general connected in series or parallel as a conversion device that converts photo energy into electrical energies. Conventionally, the energy generated by the photovoltaics are either used directly as a power source or fed back into a local power grid thus reducing the load of the central power plant. Since solar energy can be generated only during the daytime, more power has to be generated by the central power plant during the nighttime, especially in the evening, in order to meet the demand for electrical energy. Nonetheless, the reliance of an inverter that converts DC power into the AC power may suffer from significant power loss owing to the instability of the DC power source (from the photovoltaics) and the phase tune problem (the consistency of AC power generated by the inverter in phase with the AC power in the grid). As a result, an efficient energy storage system is proposed for resolving the problems mentioned above.
In the present invention, an electrical storage system consists of a plurality of batteries connected in parallel integrated with one or more inverters. The inverters are independent from each other and each inverter is connected to at least one battery module being connected in parallel. The maximum power limit of an inverter is designed to be consistent with the power capacity of a battery module being connected with the inverter (e.g. same power rating limit is required for both the battery module and the inverter) thus assuring safe operation. Each inverter converts a DC source (from a battery) to AC power until a battery low voltage is reached. During a battery low voltage period, grid power is used for satisfying a users' demands until a pre-set battery charging time period (e.g. mid-night to 6:00 AM) is reached. Each inverter can be connected to a circuit breaker already installed in an office or a home. The storage system presently disclosed can be installed easily in a home or office and can be integrated with solar panels, wind turbines or other renewable energy sources for energy saving purposes that will be illustrated in later examples.